January 1, 2026
Description
The Mijia LYWSD03MMC temperature / humidity sensor is tiny and works great. The battery life is fine, but what if it was even better? This is a modification to the battery tray to accept a CR2450 battery, which increases the battery capacity to approximately 2.7x the original.
CR2032 Typical Capacity: 225 mAh
CR2450 Typical Capacity: 610 mAh
This only works with Mijia sensors with no components on the back of the PCB. The most recent revision has a button and chip which are in the way of the space required for the larger battery.
✅ Compatible | ❌ Not compatible |
To ensure the clip and clip-cut outs work correctly, I recommend printing at fine layer settings with a 0.4mm nozzle. 0.12mm layer height worked well for me.
4 top and bottom layers, 2 walls and 5% infill is plenty.
Use Inner-Outer-Inner walls to get the highest precision outer walls to ensure the clip areas print best.
Print upside-down with supports around the screw holes and at the bottom. All other areas will bridge fine without supports.
Pull the back cover off the sensor
Remove the battery
Unscrew the screws (a tiny torx driver is required - unsure which size, less than T6)
Pull the battery tray out
Replace with the new tray
Cover up Gnd, Reset, P3 pads with tape
Re-install screws
Remove foam pad from back cover and discard (or re-use on your cabinet doors!)
Insert CR2450
Re-install back cover - note that the cover holds the battery in place now.
Cover Gnd, Reset, P3 pads with tape
Remove foam pad and discard (or re-use on your cabinet doors!)
License:
Creative Commons — Attribution
9
Kizzard
